Seasonal Prediction of the Quasi-Biennial Oscillation

The ability to forecast the Quasi-Biennial Oscillation (QBO) was examined using Version 2 of NASA's Global Earth Observing System Subseasonal-to-Seasonal (GEOS-S2S) forecasting system. The vertical and time structure of the QBO was characterized by the principal components of the first two empirical orthogonal functions (EOFs). A set of 9-month retrospective forecasts was initialized four times each month between 1981 and early 2019. Validation of 1-9 months forecasts from GEOS-S2S showed that the S2S retrospective QBO forecasts improved skill in predicting the QBO EOF-based amplitude and phase over a simple QBO phase propagation model at forecast lead times of 1-3 months. Results from an initial assessment of whether more accurate QBO forecasts can improve Northern Hemisphere winter sea level pressure forecasts showed no significant forecast improvement at a 1-month lead time, indicating the need for improved stratosphere-troposphere QBO coupling metrics, pathway identification, and QBO modeling. Overall, these results suggest that future improvements in representing the QBO in global models can increase the skill of 1-3 months QBO forecasts and potentially extend useful QBO forecasts beyond 3 months.